Evaluation of asphalt binder and mixture properties utilizing fish scale powder as a biomodifier

Fish represent an abundant and underutilized waste product from the fishing industry. This study investigated the effects of incorporating fish scale powder (FSP) at various dosages (3%, 6%, 9%, and 12%) on the properties of asphalt binder and mixtures. Conventional tests, viscosity, storage stability, Fourier transform infrared spectroscopy, and multiple stress creep recovery tests were conducted on the binder. Mix design, wheel tracking, indirect tensile strength, fatigue, and ultrasonic pulse velocity tests were evaluated for the asphalt mixtures. The results showed that FSP increased binder stiffness and reduced temperature susceptibility but compromised low-temperature performance and workability regardless of dose. The storage stability test results showed improved high-temperature storage stability. In the mixtures, the permanent deformation resistance increased with increasing FSP content, decreasing the rut depth from 4.3 mm for the control to 2.9 mm at 12% FSP. The moisture damage resistance, indicated by the tensile strength ratio, increased from 90% for the control to 94.1% at 12% FSP. However, the fatigue life decreased from 14,010 cycles for the control sample to 11,190 cycles at 12% FSP. The dynamic and elastic modulus values before conditioning increased with higher FSP dosages, and this increasing trend was also observed after conditioning, signifying greater stiffness retention and moisture resistance of the asphalt mixtures containing higher amounts of FSP. Numerically, the 6-9% FSP range offered the optimum balance, enhancing the rutting resistance by 18% and moisture resistance by 3.2% compared to those of the control, while limiting the fatigue life to 12% and maintaining the workability. Overall, fish scale powder has potential for use as an asphalt biomodifier by transforming an environmental liability into a value-added sustainable paving material.